The development of end-organ pathology in primary hypertension is a multifactorial process. While blood pressure elevation clearly plays a role, other factors which are poorly understood, also appear to be involved. There have been few studies to determine these other factors in children and adolescents with essential hypertension. The principal investigator has recently completed a cross-sectional study of the correlates of left ventricular hypertrophy (determined by echocardiography), glomerular hyperfiltration measured by creatinine clearance, and retinal vascular abnormalities observed on photographs of the optic fundus in this population. This application proposes a prospective longitudinal study of children and adolescents with essential hypertension to investigate the temporal relationships between the change in potential risk factors (correlates) identified in the previous study and the development and progression of the target organ abnormalities. The risk factors associated with the development of end organ abnormalities in one organ system will be compared to the factors associated with abnormalities in the other organ systems. The proposed study will utilize a radioisotope study to determine glomerular filtration rate. This research will also test the hypotheses that left ventricular hypertrophy is detrimental to cardiac performance, and that the rate of urinary albumin excretion is correlated with glomerular filtration rate and is an indicator of nephrosclerosis. The ultimate goal of this investigation is to provide better understanding of the pathophysiologic processes involved in the development of heart, kidney and eye end-organ pathology. This may provide the basis for improved strategies to prevent target-organ abnormalities in children, adolescents and young adults with essential hypertension.